PROJECT SUMMARY Exposure to environmental concentrations of pesticides and metals can cause neurobehavioral changes that influence survival of Pacific salmon. These neurological impacts that arise from central and peripheral nervous system deficits, including inhibition of peripheral olfactory function, may block the ability to detect predators and prey, alter reproductive timing, and interfere with homing to natal streams. The fish peripheral olfactory system is highly vulnerable to the toxic effects of dissolved contaminants due to its direct contact with the aquatic environment. Olfactory injury is now documented in other aquatic species exposed to environmental pollutants, suggesting far-reaching ecological ramifications of this phenomenon. The goal of our project is to understand the mechanisms of chemical-induced olfactory injury in Pacific salmon, and based upon our findings, generate biomarkers of olfactory injury to evaluate the ecological health and remediation outcomes at Superfund sites. Our studies will also use zebrafish, a well-defined genetic model, to better understand the mechanisms of olfactory injury that are relevant to salmon. In the current application, we will continue to integrate molecular, biochemical, physiological, and behavioral endpoints using model metal olfactory toxicants that are relevant to Superfund exposures. This novel approach allows a thorough understanding of mechanisms of chemical- induced olfactory injury in fish. In Aim 1, we will use salmon and several transgenic zebrafish lines to identify olfactory receptor neuron populations that are targets of cadmium (Cd) and address impaired olfactory signaling and neuron regeneration (neurogenesis) as mechanisms of Cd-mediated olfactory injury. We will also use transgenic zebrafish to evaluate the potency of other Superfund metals as olfactory toxicants. In Aim 2, we will investigate transcriptional and post-transcriptional control of olfaction during metal exposures. We will identify functionally important olfactory microRNAs (miRNAs) and their gene targets that are essential regulators of metal-induced olfactory injury. In Aim 3, we will test glutathione S-transferase (GST) isoforms as biomarkers of olfactory injury, and investigate the mechanisms of Nrf2 in olfactory neuroprotection. We will then incorporate our most robust olfactory molecular biomarkers to evaluate remediation outcomes in the lower Duwamish waterway, a regional Superfund site at various stages of remediation. We have assembled a strong team of collaborators for this project whose interactions are described in the proposal. We have endeavored to be responsive to SRP objectives by using mechanistic approaches to address ecological and human health hazards, as well as remediation outcomes at Superfund sites. Our studies involve strong partnerships with WA State and federal agencies involved in Superfund site assessment, and with community stakeholders affected by hazardous wastes.